1. Field of the Invention
The present invention is applicable to a facsimile machine, a printer, a photocopier or a combination of these machines and is directed to an image forming apparatus wherein toner powder is used for image development. More particularly, the present invention relates to a toner storage unit for feeding toner into a developer unit, a residual toner collect unit for collecting residual toner after the image has been developed, a toner container wherein the toner storage unit and the residual toner collect unit are integrated together, and an image forming apparatus including one of these units.
2. Description of the Related Art
An image forming system is conventionally used as a facsimile machine, a printer and a photocopier, and for example, includes an electrophotographic apparatus and an electrostatic recording apparatus as an indirect toner image recording system. These apparatus typically employs a photosensitive drum or belt. A latent image is formed on the photosensitive element by an exposure unit and then, turned to a developed or toner powder image by a developer unit. The toner powder image is thereafter transferred from the photosensitive element to a sheet of recording paper. Also, a direct toner image recording system is well known (see WO 90/14959) and includes a mesh electrode arranged in matrix form and disposed between a toner carrier roller and a back electrode for allowing the passage of a recording paper. A voltage is applied, in a controlled manner, to the mesh electrode corresponding to video or image data so as to attach a toner image to a sheet of recording paper directly from the toner carrier roller.
In such a recording system, for example, the electrophotographic apparatus, a separate toner storage unit provides a toner receptacle in the developer unit with a fresh supply of toner when the toner receptacle becomes empty as a result of consumption of the toner on the photosensitive drum.
More specifically, the toner receptacle in the developer unit has an open top. The toner storage unit has an open bottom which is engageable with the open top of the toner receptacle and sealed by a peelable sheet or a closure member. After the toner storage unit is engaged with the top opening of the toner receptacle, the peelable sheet is peeled off or the closure member is opened so as to dispense the toner from the toner storage unit into the toner receptacle through the open bottom of the toner storage unit and the open top of the toner receptacle.
However, the peelable sheet is subject to damage due to shock in shipment or handling. Also, the open bottom of the toner storage unit is always kept open after the peelable sheet has been peeled away from the open bottom. Thus, residual toner may be scattered from the open bottom of the toner storage unit and may cause soiling within the machine when the toner storage unit is removed from the toner receptacle.
There has been proposed a device wherein shutter members are mounted to the supply opening of the toner storage unit and the opening of a toner receptacle. These openings are opened with the opening of a separate or single shutter member (see Japanese laid-open utility model publication No. 50-84056 and Japanese utility model publication No. 55-12193).
In such a device, toner particles fall into the toner receptacle and are attached to the open edge of the toner receptacle as the shutter members are opened. The toner particles tend to be scatterd from the open edge to cause slight soiling within the machine when the toner storage unit is removed.
The separate shutter member is typically pulled in the longitudinal direction of the toner storage unit. Its operation thus requires a unduly long space.
In order to solve such problems, Japanese laid-open utility model publication No. 5-84966 discloses a toner storage unit which has a shutter member at its bottom and is located adjacent the toner receiving opening of a machine body. When the shutter member of the machine body is pulled (with the shutter member of the toner storage unit being fixed), the toner storage unit or body is so moved as to face with the toner receiving opening of the machine body. This causes toner in its entirety to be drained from the toner storage unit into the machine body.
However, as the toner in its entirety within the toner storage unit falls into the machine body, the machine body must have such a volume as to prevent overflow of the toner. This results in an increase in the size of the machine body.
Where a developer material has two different components, it is necessary to provide a developer unit with a plurality of chambers, that is, a hopper for containing toner and a T/C container for agitating carrier particles and toner particles. If the hopper is adapted to receive the toner in its entirety, there is a substantial difference in quantity between when the hopper is empty and when the hopper is full. This arrangement makes it difficult to control a supply of toner to the T/C container.
Also, discharge of the entire toner at once has a detrimental effect on image development since some of the toner is subject to caking or agglomeration and is drained, in that state, into the hopper.
To overcome such deficiency, the toner storage unit has a side wall extending upwardly from its bottom. An opening is formed in the side wall, and a agitator blade is attached to a rotary shaft which extends along the length of the toner storage unit. The agitator blade is curved from the bottom toward the opening with a predetermined radius of curvature and is rotated to break the agglomerated toner and scrape the toner from the inner wall of the toner receptacle. In this way, the toner is drained from the bottom of the toner storage unit through the opening into the toner receptacle.
The inner wall of the toner receptacle on which the agitator blade is frictionally slid is so arcuated as to provide uniform axial torque. This arragement, however, results in unform linear velocity of the agitator blade. It is thus difficult to effectively scrape the toner from the bottom of the toner storage unit up to the opening when the amount of the toner within the toner storage unit decreases, in other words, when the toner is accumulated only in the bottom of the toner storage unit.
To this end, the toner storage unit may have a larger opening. In such a case, however, a substantial amount of toner will be discharged at the initial stage of agitation. It is thus impossible to achieve desired results in this art, that is, gradual supply of toner.
Also, the linear velocity of the agitator blade may be increased as the amount of toner contained within the toner storage unit is decreased. However, this attempt is not appropriate since to increase the linear speed along the entire circumference brings about an increase in axial torque. In addition, the axial torque and the linear velocity are unduly increased at the initial stage of agitation where the toner storage unit has a large amount of toner.
In the electrophotographic apparatus, a cleaning blade is employed to remove residual toner from the photosensitive drum after the toner has been transferred. The residual toner is then directed to a collect container by conveyance means. The collect container is provided at one end of a drum shaft.
In the direct recording system, residual toner is removed from the mesh electrode by an electrostatic, hydraulic or a mechanical cleaning means and is directed to a collect container.
It is necessary to replace the collect container when a predetermined number of copies are produced. However, a indication of required replacement is generally not shown on a display or similar means. There is a risk of overflow as a result of continued production of copies because an operator is not aware of the fact that the collect container is full up with residual toner. As this occurs, the machine suffers from soiling.
In order to overcome this disadvantage, the collect container may have a larger volume. However, such a large collect container substantially affects the design of the machine since the machine has a limited space. It also contradicts the need for a compact machine.
To this end, there have been proposed various devices (see Japanese laid-open patent publication No. 2-33168 and other publications) wherein a toner storage unit and a toner collect container are integrated as a single unit (hereinafter, referred to as a toner container). This arrangement allows replacement of the toner collect container simultaneously or automatically when the toner storage unit is replaced.
One example of such toner container is disclosed, for example, in Japanese laid-open patent publication No. 2-33168. A toner container comprises a cylindrical toner storage unit within which a partition is provided to difine a residual toner collect section at one longitudinal end of a toner reservoir. Another example is disclosed in Japanese laid-open patent publication No. 5-88423. This toner container includes a toner storage unit and a toner collect container with a toner conveyance means, which are integrated by a connecting shaft to form a kit.
However, either of these conventional toner containers is loaded to and unloaded from a machine body in the axial direction of the photosensitive drum or the longitudinal direction of the toner container. A large space is inevitably required for replacement of the toner containers. Particularly, the total length of the toner container is unduly increased since the toner container includes a residual toner collect section at the longitudinal end of the toner reservoir.
In a printer or similar machine where there is no need to provide a document table, it has been proposed that the top of the machine which faces with a document unit can be opened to allow a toner container to be loaded to and unloaded from the top of the machine in the width direction of the toner container, in other words, in a direction at right angles to the axis of the photosenstive drum.
However, this results in a decrease in the width of a guide, as compared to the manner in which the toner container is loaded to the developer unit in the longitudinal direction of the toner container. It is thus impossible to accurately load the container to the developer unit.
The residual toner is not given a uniform charge due to corona discharge or other reasons when an electrostatic latent image is formed, when a bias is applied, or when an image is transferred. As a result, the residual toner is not uniformly accumulated within the toner collect container and tends to be accumulated adjacent the opening of the toner collect container. The residual toner is also subject to crosslinking as it is charged. This results in a decrease in the bulk density of the toner.
As such, even if the toner collect container is designed to become full up with the toner at the time of replacement of the toner container, overflow of the residual toner results prior to the replacement. As this occurs, the machine suffers from soiling.
To prevent uneven accumulation and crosslinking of the residual toner, attemtps have previously been made to provide an agitator blade within a residual toner collect container. However, rotation of the agitator blade within a space wherein residual toner is accumulated results in an increase in the required power. Also, the residual toner, when agitated, is sometimes discharged from the container to outside a residual toner receiving opening.
In view of the foregoing, the inventor of the present application previously proposed an ellipsoidal conveyance roller provided adjacent to the opening of a residual toner collect chamber. Residual toner enters through the opening and is forced toward the residual toner collect chamber as the conveyance roller is rotated (see Japanese utility model application No. 4-29320).
The conveyance roller provides a large force, but can convey only a small amount of residual toner. To this end, an element made of Mylar (TM) is provided to divide the interior of the collect chamber into a preliminary chamber and an accumulation chamber. Residual toner is first drained through the opening into the preliminary chamber. The residual toner is then forced into the accumulation chamber as the conveyance roller is rotated. Even with this arrangement, the residual toner still tends to be accumulated only in the inlet of the accumulation chamber. This results in an increase in useless space of the chamber.
Given the volume of a hopper in a developer unit, it is preferable to gradually add toner contained in the toner storage unit while the toner is agitated by the agitator blade. It is also necessary to provide the residual toner collect chamber with an agitation blade in order to prevent uneven accumulation and crosslinking of the residual toner and insure effective accumulation. In this case, there must be provided an effective seal between the partition and the rotary shaft which extends through the partition. Otherwise, not only the power of the shaft is undesirably increaesd, but also the residual toner enters the collect container.